1. Field of the Invention
The present invention relates in general to automotive power pivot doors, and more particularly to control devices of the automotive power pivot doors. More specifically, the present invention is concerned with a control device that controls upward/downward pivot movement of an automotive back door driven by an electric motor with an aid of a clutch.
2. Description of Related Art
Hitherto, various automotive power pivot doors have been proposed and put into practical use particularly in the field of wheeled motor vehicles.
Some of them are of a type that has both an automatic mode wherein an open/close movement of an automotive back door is carried out automatically with a power of an electric motor and a manual mode wherein the open/close movement of the back door is carried out manually without the aid of the power of the electric motor.
For achieving the two modes, there is usually employed an electromagnetic clutch through which the electric motor and the back door are selectively connected. That is, in the automatic mode, the clutch takes an engaged condition, so that the power of the motor is transmitted to the back door through the engaged clutch, while, in the manual mode, the clutch takes a disengaged condition, and thus the manual open/close movement of the back door is carried out without obstruction from the electric motor. Actually, there is further employed a speed reducing mechanism which, to increase a power for lifting up the back door, outputs a rotation of which speed is lower than that of the motor.
For keeping the back door at its full-open position, there are usually employed gas stays that support the weight of the back door with a force of compressed gas. However, if the gas stays fail to operate due to long use or damage of the same, it may occur that the back door assuming the full-open position falls down suddenly upon disengagement of the clutch, which is of course an undesirable movement.
For solving the above-mentioned undesired sudden falling of the back door, a measure is proposed by Japanese Laid-open Patent Application (Tokkai) 2001-107642. That is, in the measure, there is provided a control device which, upon sensing a sign of the falling of the back door, forces the clutch to take the engaged condition thereby stopping the falling of the back door by a marked resistance produced in a torque transmitting path from the motor to the back door.